class_docstr: Performs model confidence checks.
  
  Checks performed:
  
  * `NormalizationBiasVerification` for detecting invalid combinations of
     bias and normalization layers.
     See `allennlp.confidence_checks.normalization_bias_verification` for more details.
  
  Note: Any new confidence checks should also be added to this callback.
code: def on_start(
      self,
      trainer: "GradientDescentTrainer",
      is_primary: bool = True,
      **kwargs,
  ) -> None:
      self.trainer = trainer
      if is_primary:
          self._verification = NormalizationBiasVerification(
              self.trainer._pytorch_model
          )
          # Register the hooks that perform the verification before training starts.
          self._verification.register_hooks()
  
file_path: allennlp/allennlp/training/callbacks/confidence_checks.py
imports: from typing import List, Dict, Any, Optional, TYPE_CHECKING
  from allennlp.training.callbacks.callback import TrainerCallback
  from allennlp.data import TensorDict
  from allennlp.confidence_checks.normalization_bias_verification import NormalizationBiasVerification
label_desc: Use image node_id 1 for calling the ConfidenceChecksCallback obj's underlying member method code with example usage: obj.on_start(trainer, is_primary) without return types